drm/xe: implement driver initiated function-reset

Driver initiated function-reset (FLR) is the highest level of reset
that we can trigger from within the driver. In contrast to PCI FLR it
doesn't require re-enumeration of PCI BAR. It can be useful in case
GT fails to reset. It is also the only way to trigger GSC reset from
the driver and can be used in future addition of GSC support.

v2:
  - use regs from xe_regs.h
  - move the flag to xe.mmio
  - call flr only on root gt
  - use BIOS protection check
  - copy/paste comments from i915
v3:
  - flr code moved to xe_device.c
v4:
  - needs_flr_on_fini moved to xe_device

Signed-off-by: Andrzej Hajda <andrzej.hajda@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/regs/xe_regs.h

@@ -70,8 +70,15 @@
 
 #define SOFTWARE_FLAGS_SPR33			XE_REG(0x4f084)
 
+#define GU_CNTL_PROTECTED			XE_REG(0x10100C)
+#define   DRIVERINT_FLR_DIS			REG_BIT(31)
+
 #define GU_CNTL					XE_REG(0x101010)
 #define   LMEM_INIT				REG_BIT(7)
+#define   DRIVERFLR				REG_BIT(31)
+
+#define GU_DEBUG				XE_REG(0x101018)
+#define   DRIVERFLR_STATUS			REG_BIT(31)
 
 #define XEHP_CLOCK_GATE_DIS			XE_REG(0x101014)
 #define   SGSI_SIDECLK_DIS			REG_BIT(17)

drivers/gpu/drm/xe/xe_device.c

@@ -5,6 +5,8 @@
 
 #include "xe_device.h"
 
+#include <linux/units.h>
+
 #include <drm/drm_aperture.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_gem_ttm_helper.h>
@@ -252,6 +254,78 @@ struct xe_device *xe_device_create(struct pci_dev *pdev,
 	return ERR_PTR(err);
 }
 
+/*
+ * The driver-initiated FLR is the highest level of reset that we can trigger
+ * from within the driver. It is different from the PCI FLR in that it doesn't
+ * fully reset the SGUnit and doesn't modify the PCI config space and therefore
+ * it doesn't require a re-enumeration of the PCI BARs. However, the
+ * driver-initiated FLR does still cause a reset of both GT and display and a
+ * memory wipe of local and stolen memory, so recovery would require a full HW
+ * re-init and saving/restoring (or re-populating) the wiped memory. Since we
+ * perform the FLR as the very last action before releasing access to the HW
+ * during the driver release flow, we don't attempt recovery at all, because
+ * if/when a new instance of i915 is bound to the device it will do a full
+ * re-init anyway.
+ */
+static void xe_driver_flr(struct xe_device *xe)
+{
+	const unsigned int flr_timeout = 3 * MICRO; /* specs recommend a 3s wait */
+	struct xe_gt *gt = xe_root_mmio_gt(xe);
+	int ret;
+
+	if (xe_mmio_read32(gt, GU_CNTL_PROTECTED) & DRIVERINT_FLR_DIS) {
+		drm_info_once(&xe->drm, "BIOS Disabled Driver-FLR\n");
+		return;
+	}
+
+	drm_dbg(&xe->drm, "Triggering Driver-FLR\n");
+
+	/*
+	 * Make sure any pending FLR requests have cleared by waiting for the
+	 * FLR trigger bit to go to zero. Also clear GU_DEBUG's DRIVERFLR_STATUS
+	 * to make sure it's not still set from a prior attempt (it's a write to
+	 * clear bit).
+	 * Note that we should never be in a situation where a previous attempt
+	 * is still pending (unless the HW is totally dead), but better to be
+	 * safe in case something unexpected happens
+	 */
+	ret = xe_mmio_wait32(gt, GU_CNTL, DRIVERFLR, 0, flr_timeout, NULL, false);
+	if (ret) {
+		drm_err(&xe->drm, "Driver-FLR-prepare wait for ready failed! %d\n", ret);
+		return;
+	}
+	xe_mmio_write32(gt, GU_DEBUG, DRIVERFLR_STATUS);
+
+	/* Trigger the actual Driver-FLR */
+	xe_mmio_rmw32(gt, GU_CNTL, 0, DRIVERFLR);
+
+	/* Wait for hardware teardown to complete */
+	ret = xe_mmio_wait32(gt, GU_CNTL, DRIVERFLR, 0, flr_timeout, NULL, false);
+	if (ret) {
+		drm_err(&xe->drm, "Driver-FLR-teardown wait completion failed! %d\n", ret);
+		return;
+	}
+
+	/* Wait for hardware/firmware re-init to complete */
+	ret = xe_mmio_wait32(gt, GU_DEBUG, DRIVERFLR_STATUS, DRIVERFLR_STATUS,
+			     flr_timeout, NULL, false);
+	if (ret) {
+		drm_err(&xe->drm, "Driver-FLR-reinit wait completion failed! %d\n", ret);
+		return;
+	}
+
+	/* Clear sticky completion status */
+	xe_mmio_write32(gt, GU_DEBUG, DRIVERFLR_STATUS);
+}
+
+static void xe_driver_flr_fini(struct drm_device *drm, void *arg)
+{
+	struct xe_device *xe = arg;
+
+	if (xe->needs_flr_on_fini)
+		xe_driver_flr(xe);
+}
+
 static void xe_device_sanitize(struct drm_device *drm, void *arg)
 {
 	struct xe_device *xe = arg;
@@ -283,6 +357,10 @@ int xe_device_probe(struct xe_device *xe)
 	if (err)
 		return err;
 
+	err = drmm_add_action_or_reset(&xe->drm, xe_driver_flr_fini, xe);
+	if (err)
+		return err;
+
 	for_each_gt(gt, xe, id) {
 		err = xe_pcode_probe(gt);
 		if (err)

drivers/gpu/drm/xe/xe_device_types.h

@@ -388,6 +388,9 @@ struct xe_device {
 	/** @heci_gsc: graphics security controller */
 	struct xe_heci_gsc heci_gsc;
 
+	/** @needs_flr_on_fini: requests function-reset on fini */
+	bool needs_flr_on_fini;
+
 	/* For pcode */
 	struct mutex sb_lock;
 

drivers/gpu/drm/xe/xe_gt.c

@@ -626,6 +626,8 @@ static int gt_reset(struct xe_gt *gt)
 	xe_uevent_gt_reset_failure(to_pci_dev(gt_to_xe(gt)->drm.dev),
 				   gt_to_tile(gt)->id, gt->info.id);
 
+	gt_to_xe(gt)->needs_flr_on_fini = true;
+
 	return err;
 }